An insurer may invest in the securities of any open end management type investment company, investment trust or mutual fund registered with the United States securities and exchange commission or in a common trust fund of a bank regulated by a federal or state agency within the limitations prescribed by this article if the investments held by the investment company or common trust fund, if added to the assets of the insurer on a basis that is in the same proportion that the shares of the investment company or investments in a common trust fund held by the insurer bear to all of the shares of the investment company or investments in a common trust fund outstanding, would not cause the insurer to exceed the limitations contained in this article.